Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and delivers: idempotency semantics (concurrent duplicates rejected server-side), transactional rollback of the charge on failure, quota/balance enforcement, a site-wide enablement gate, NS requirements with the externalNsForbidden exception and automatic site-DNS wiring, tiered pricing/renewal rules, and IDN/punycode rejection. This is unusually rich disclosure of what happens around the call.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Core action is front-loaded in the first clause, and nearly every sentence carries distinct operational information with no filler. It is delivered as one dense block, though, and would be easier to scan if the NS/pricing/IDN rules were separated rather than run together.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a complex mutation tool with no annotations and no output schema, the description covers idempotency, rollback, quotas, NS rules, pricing tiers, and IDN restrictions well. It omits any indication of what a successful registration returns and does not elaborate on the DNSSEC/dsRecords path, which is left to the schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 83%, so the schema does most of the work, but the description adds genuine meaning the schema lacks: the externalNsForbidden interaction that makes nameservers invalid for certain suffixes, the predefined-provider vs custom NS options, and the label-length pricing/IDN constraints on `label`. It stops short of clarifying dsRecords behavior beyond what the schema already says.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Opens with a specific verb+resource ("Register a subdomain under a suffix") and immediately adds the consequential side effect ("charge points"), which cleanly separates it from domain_renew, domain_transfer_*, and domains_check. It never names those siblings explicitly, so the differentiation is inferable from the verb rather than stated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description supplies strong preconditions (site-wide registration enabled, per-user quota and balance enforced) but frames them as failure conditions rather than as guidance on when to pick this tool over alternatives like domain_renew for existing domains or domains_check for availability. Usage is implied by the verb, not routed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.